One cannot plead guilty and then elect to go to Crown Court. That option is only available in the event of a Not Guilty plea and where the Magistrates have decided to accept jurisdiction..
If he pleaded guilty it is solely a matter for the Magistrates to decide whether to sentence him theirselves or to send him to the Crown Court for sentence if they consider their sentencing powers are insufficient.
Please find out what really happened as this has a considerable bearing on the likely outcome.